WO2015152088A1 - Carbonaceous material for non-aqueous electrolyte secondary battery negative electrode, negative electrode for non-aqueous electrolyte secondary battery, non-aqueous electrode secondary battery, and vehicle - Google Patents

Abstract

The present invention provides a carbonaceous material for a non-aqueous electrolyte secondary battery negative electrode, said material having a high discharge capacity per volume and excellent storage characteristics. In this carbonaceous material for a non-aqueous electrolyte secondary battery negative electrode, the true density (ρ_Bt) determined by a butanol method is at least 1.55 g/cm³ but less than 1.75 g/cm³, and the discharge capacity of the negative electrode from 0.05-1.5 V in terms of a lithium reference electrode is at least 180 mAh/g. Furthermore, the slope (0.9/X (Vg/Ah)) of the discharge curve, which is calculated from the discharge capacity (X (Ah/g)) and potential difference (0.9 (V)) that correspond to 0.2-1.1 V in terms of the lithium reference electrode, is at most 0.75 (Vg/Ah), and the moisture absorption after 100 hours of storage in a 25 °C, 50% RH air environment is at most 1.5 wt%.

Description

Non-aqueous electrolyte secondary battery negative electrode carbonaceous material, non-aqueous electrolyte secondary battery negative electrode, non-aqueous electrolyte secondary battery and vehicle

The present invention relates to a carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode, a negative electrode for a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery, and a vehicle.

In recent years, due to increasing interest in environmental issues, the installation of large lithium ion secondary batteries with high energy density and excellent output characteristics in electric vehicles is being studied. In particular, an in-vehicle lithium ion secondary battery is large and expensive, and is difficult to replace on the way. Accordingly, at least the same durability as that of an automobile is required, and realization of a life performance of 10 years or more (high durability) is required. In the case of graphite materials, negative electrode materials for in-vehicle lithium ion secondary batteries that require high cycle durability because they are prone to breakage due to expansion and contraction of crystals due to repeated lithium doping and dedoping, and poor charge / discharge performance. Not suitable for. On the other hand, carbonaceous materials such as non-graphitizable carbon whose graphite structure is not highly developed are small in terms of expansion and contraction of particles due to lithium doping and dedoping reactions, and have high cycle durability. Suitable for use in automotive applications.

Also, in recent lithium-ion secondary batteries for in-vehicle use, it is necessary to increase the discharge capacity in order to extend the cruising distance by one charge and further improve the vehicle fuel consumption. Furthermore, since there is a high need to reduce the space on the battery, there is a demand for improvement in discharge capacity per volume. As means for increasing the capacity, it is known to promote the development of pores by performing firing in a reduced pressure or chlorine atmosphere in the production process of the carbonaceous material (Patent Documents 1 and 2). However, carbonaceous materials produced by these production methods are inferior in storage stability. On the other hand, it has been proposed that the storage stability is improved by increasing the number of closed pores of the carbonaceous material (Patent Document 3), but the undesirable result is that the capacity is greatly reduced.

Japanese Patent No. 3427577 Japanese Patent No. 3565994 JP 2003-328911 A

An object of the present invention is to provide a non-aqueous electrolyte secondary battery negative electrode carbonaceous material having a high discharge capacity per volume and excellent storage characteristics, a negative electrode for a non-aqueous electrolyte secondary battery, and a negative electrode for the non-aqueous electrolyte secondary battery. A non-aqueous electrolyte secondary battery including the vehicle and a vehicle are provided.

In the carbonaceous material in which the true density (ρ _Bt ) obtained by the butanol method is 1.55 g / cm ³ or more and less than 1.75 g / cm ³ , the present inventors have used a lithium reference electrode standard of 0.2 V to 1. When the slope of the discharge curve 0.9 / X (Vg / Ah) calculated from the discharge capacity X (Ah / g) of 1 V and the potential difference 0.9 (V) is large, the moisture absorption is high despite the high discharge capacity. As a result, it has been found that a carbonaceous material having excellent storage characteristics is provided, and the present invention has been completed. Specifically, the present invention provides the following.

(1) True density (ρ _Bt ) determined by the butanol method is 1.55 g / cm ³ or more and less than 1.75 g / cm ³ , and 0.05 V to 1.5 V negative electrode discharge capacity is 180 mAh / g based on a lithium reference electrode. The slope of the discharge curve 0.9 / X (Vg / V) calculated from the discharge capacity X (Ah / g) of 0.2 V to 1.1 V and the potential difference 0.9 (V) based on the lithium reference electrode. Ah) is 0.75 (Vg / Ah) or less, and the carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode has a moisture absorption amount of 1.5 wt% or less after 100 hours storage at 25 ° C. and 50% RH air atmosphere.

(2) The carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to (1), wherein the true density (ρ _He ) obtained by the helium substitution method is 1.76 g / cm ³ or more.

(3) [rho _{the He} and [rho _Bt and the ratio (ρ _He / ρ _Bt) is a non-aqueous electrolyte secondary battery negative electrode carbonaceous material according to (1) or (2) is 1.10 or more.

(4) When the specific surface area (BET) (unit: m ² / g) determined by the BET method by adsorption of nitrogen gas and the average particle diameter (unit: μm) are _Dv50 , the calculation formula “6 / ( The specific surface area ratio (BET / CALC) with _respect to the specific surface area (CALC) (unit: m ² / g) determined from “D _v50 × ρ _Bt ” ”is more than 5.5, from (1) to (3) above The carbonaceous material for non-aqueous electrolyte secondary battery negative electrode in any one.

(5) The carbonaceous material for a non-aqueous electrolyte secondary battery negative electrode according to any one of (1) to (4), wherein the average particle size is 1 to 15 μm.

(6) A negative electrode for a non-aqueous electrolyte secondary battery comprising the carbonaceous material for a non-aqueous electrolyte secondary battery negative electrode according to any one of (1) to (5) above.

(7) A nonaqueous electrolyte secondary battery comprising the negative electrode for a nonaqueous electrolyte secondary battery described in (6) above.

(8) A vehicle equipped with the nonaqueous electrolyte secondary battery described in (7) above.

According to the present invention, in a carbonaceous material having a true density (ρ _Bt ) determined by a butanol method of 1.55 g / cm ³ or more and less than 1.75 g / cm ³ , 0.2 V to 1. Since the discharge curve slope 0.9 / X (Vg / Ah) calculated from the discharge capacity X (Ah / g) up to a potential of 1 V and the potential difference 0.9 (V) is low, the discharge capacity is increased. Nevertheless, the carbonaceous material is low in hygroscopicity and, as a result, has excellent storage characteristics.

Hereinafter, embodiments of the present invention will be described.

[1] Non-aqueous electrolyte secondary battery negative electrode carbonaceous material The non-aqueous electrolyte secondary battery negative electrode carbonaceous material of the present invention has a true density (ρ _Bt ) of 1.55 g / cm ³ or more determined by a butanol method. Less than .75 g / cm ³ , the discharge capacity of the negative electrode of 0.05 V to 1.5 V on the basis of the lithium reference electrode is 180 mAh / g or more, and the discharge capacity X (Ah / L) of 0.2 V to 1.1 V on the basis of the lithium reference electrode g) The slope (0.9 / X) of the discharge curve calculated from the potential difference 0.9 (V) is 0.75 (Vg / Ah) or less, and it is stored for 100 hours in an air atmosphere at 25 ° C. and 50% RH. The subsequent moisture absorption is 1.5 wt% or less.

The true density (ρ _Bt ) determined by the butanol method is as high as 1.55 g / cm ³ or more and less than 1.75 g / cm ³ , and the discharge capacity of the negative electrode of 0.05 V to 1.5 V is 180 mAh based on the lithium reference electrode. In a carbonaceous material that is greater than or equal to 1 / g, the slope 0.9 / X of the discharge curve calculated from a discharge capacity (X) of 0.2 V to 1.1 V and a potential difference of 0.9 V with respect to the lithium reference electrode is 0.00. When it is 75 (Vg / Ah) or less, the slope of the discharge curve per volume in the potential range most used in the in-vehicle lithium ion secondary battery of 0.2 V to 1.1 V based on the lithium reference electrode becomes gentle. Thereby, in a practical state used in a charging range of around 50%, the potential difference between the negative electrode and the positive electrode is kept high, and a high discharge capacity per volume can be exhibited. The discharge capacity per unit volume is calculated by the product of the discharge capacity per unit mass and the true density (ρ _Bt ) determined by the butanol method.
In non-aqueous electrolyte secondary batteries for automobiles, it is not a usage pattern in which full charge and complete discharge are repeated, but an area where the input characteristics and output characteristics are always balanced, that is, 50% when the full charge is 100%. The use form which repeats charging / discharging so that a battery state may be located in the charge area before and behind is preferable. In such a usage pattern, it is preferable to use as the negative electrode material a material in which the potential change ΔE (V) with respect to the discharge capacity X (Ah / g) greatly changes with a constant slope.

The slope 0.9 / X (Vg / Ah) of the discharge curve calculated from the discharge capacity X (Ah / g) of 0.2 V to 1.1 V and the potential difference 0.9 (V) based on the lithium reference electrode is The smaller the value, the higher the discharge capacity per volume in the inclined region where the potential changes. Therefore, it is preferably 0.75 (Vg / Ah) or less, more preferably 0.70 (Vg / Ah) or less, 0 .65 (Vg / Ah) or less.

Since ρ _Bt is related to the abundance of pores into which butanol can enter, the number of fine pores increases, the hygroscopicity increases excessively and storage stability tends to be impaired, and the discharge capacity per volume is improved. from the balance, it is preferably 1.55 g / cm ³ or more, more preferably 1.59 g / cm ³ or more and 1.61 g / cm ³ or more. On the other hand, since the increase in true density tends to be a material with high regularity of crystal structure, it is preferably 1.70 g / cm ³ or less, more preferably from the viewpoint of suppressing expansion and contraction associated with charge / discharge. Is 1.68 g / cm ³ or less.

In the carbonaceous material of the present invention, the slope of the discharge curve is 0.9 / X (calculated from a discharge capacity X (Ah) of 0.2 V to 1.1 V and a potential difference of 0.9 (V) based on the lithium reference electrode. Vg / Ah) is small and the potential changes slowly, so that the discharge capacity of the negative electrode in a practical range of 0.05 V to 1.5 V with respect to the lithium reference electrode can be obtained in a high range. Specifically, the discharge capacity of the 0.05 V to 1.5 V negative electrode based on the lithium reference electrode is preferably 180 mAh / g or more. More preferably, it is 190 mAh / g or more and 195 mAh / g or more.

The moisture absorption after 100 hours storage at 25 ° C. and 50% RH air atmosphere is preferably 1.5 wt% or less, more preferably 1.3 wt% or less, 1.0 wt% or less, 0.80 wt% or less, 0.50 wt% and 0.30 wt% or less.

In the present invention, the true density obtained by helium displacement method ([rho _{the He)} is in the respect of improving the volume per discharge capacity, is preferably 1.76 g / cm ³ or more, more preferably 1.85 g / cm ³ From the viewpoint of suppressing hygroscopicity, it is preferably 2.09 g / cm ³ or less, and more preferably 2.03 g / cm ³ or less. ρ _He depends on the number of holes that allow helium to enter. Such holes are not only relatively large holes that are greatly involved in moisture absorption, but also have a high degree of involvement in the storage and release of Li. Also included are pores that are considered. For this reason, ρ _He affects both the discharge capacity per volume and the hygroscopicity.

In the present invention, the ratio of ρ _He to ρ _Bt (ρ _He / ρ _Bt ) is determined from the balance between the point that the hygroscopic property is excessively increased and the storage stability is liable to be impaired and the discharge capacity per volume is improved. On the other hand, it is preferably 10.10 or more, preferably 1.37 or less, more preferably 1.28 or less. This ratio reflects the number of pores large enough to allow butanol to penetrate but not helium, and these pores are more involved in the occlusion and release of Li than in the moisture absorption in the atmosphere. Is considered to be high.

In the present invention, when the specific surface area (BET) (unit: m ² / g) determined by the BET method by adsorption of nitrogen gas and the average particle diameter (unit: μm) are _Dv50 , the calculation formula “6 / It is preferable that the specific surface area ratio (BET / CALC) with _respect to the specific surface area (CALC) (unit: m ² / g) obtained from (D _v50 × ρ _Bt ) ” _exceeds 5.5. While BET is determined taking into account the pores into which nitrogen gas can enter, CALC depends on ρ _Bt and therefore depends on relatively large pores to which butanol can enter. In other words, the large BET / CALC reflects the large number of pores that are incapable of entering butanol but capable of entering nitrogen, and such pores are more than the degree of moisture absorption in the atmosphere. , Li is considered to be highly involved in occlusion and release of Li. In this respect, BET / CALC is preferably 8 or more, more preferably 11 or more, and preferably 50 or less, more preferably 15 or less.

If the specific surface area (BET) determined by the BET method of nitrogen adsorption of the carbonaceous material of the present invention is too small, the discharge capacity of the battery tends to be small, so that it is 1 m ² / g or more, preferably 1.6 m ^2. / G or more, more preferably 2.0 m ² / g or more. On the other hand, when the BET specific surface area is too large, the irreversible capacity of the obtained battery tends to increase, and therefore, 25 m ² / g or less is preferable. More preferably, it is 20 m ² / g or less.

The specific surface area (CALC) obtained from the calculation formula “6 / (D _v50 × ρ _Bt )” is preferably 0.2 m ² / g or more and 1.5 m ² / g or less. If it is less than 0.2 m ² / g, the discharge capacity of the battery tends to be small, and if it exceeds 1.5 m ² / g, the resulting hygroscopicity tends to be high.

H / C of the carbonaceous material of the present invention is measured by elemental analysis of hydrogen atoms and carbon atoms. Since the hydrogen content of the carbonaceous material decreases as the degree of carbonization increases, H / C is It tends to be smaller. Therefore, H / C is effective as an index representing the degree of carbonization. Although H / C of the carbonaceous material of this invention is not limited, it is 0.10 or less, More preferably, it is 0.08 or less. Especially preferably, it is 0.05 or less. If the ratio H / C of hydrogen atoms to carbon atoms exceeds 0.1, many functional groups are present in the carbonaceous material, and the irreversible capacity may increase due to reaction with lithium, which is not preferable.

The average layer spacing of the (002) plane of the carbonaceous material shows a smaller value as the crystal perfection is higher, that of an ideal graphite structure shows a value of 0.3354 nm, and the value increases as the structure is disturbed. Tend. Therefore, the average layer spacing is effective as an index indicating the carbon structure. The average interplanar spacing of the 002 plane determined by the X-ray diffraction method of the carbonaceous material for the negative electrode of the nonaqueous electrolyte secondary battery of the present invention is 0.365 nm or more, and more preferably 0.370 nm or more. Similarly, the average spacing is 0.400 nm or less, more preferably 0.395 nm or less, and still more preferably 0.390 nm or less. When the 002 plane spacing is less than 0.365 nm, the doping capacity becomes small when used as the negative electrode of a non-aqueous electrolyte secondary battery, which is not preferable. On the other hand, if it exceeds 0.400 nm, the undedoped capacity increases, which is not preferable.

In order to improve the output characteristics, it is important to make the active material layer of the electrode thin, and for that purpose, it is important to reduce the average particle diameter. However, if the average particle size is too small, the amount of fine powder increases and safety is lowered, which is not preferable. On the other hand, if the particles are too small, the amount of binder necessary to form an electrode increases and the resistance of the electrode increases. On the other hand, when the average particle size is increased, it is difficult to apply a thin electrode, and further, the lithium free diffusion process in the particles is increased, so that rapid charge / discharge is difficult. Therefore, the average particle diameter D _v50 (that is, the particle diameter at which the cumulative volume is 50%) is preferably 1 to 15 μm, more preferably 1.5 μm to 2 μm, while 13 μm or less, 12 μm or less. It is.

The carbonaceous material for the negative electrode of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, but the firing conditions are optimized while being based on a manufacturing method similar to the conventional carbonaceous material for the negative electrode of the nonaqueous electrolyte secondary battery. Therefore, it can be manufactured satisfactorily. Specifically, it is as follows.

(Carbon precursor)
The carbonaceous material of the present invention is produced from a carbon precursor. Examples of the carbon precursor include petroleum pitch or tar, coal pitch or tar, thermoplastic resin, or thermosetting resin. In addition, as the thermoplastic resin, polyacetal, polyacrylonitrile, styrene / divinylbenzene copolymer, polyimide, polycarbonate, modified polyphenylene ether, polybutylene terephthalate, polyarylate, polysulfone, polyphenylene sulfide, fluororesin, polyamideimide, or polyether Mention may be made of ether ketones. Furthermore, examples of the thermosetting resin include phenol resin, amino resin, unsaturated polyester resin, diallyl phthalate resin, alkyd resin, epoxy resin, and urethane resin.
In the present specification, the “carbon precursor” means the carbonaceous material from the untreated carbonaceous material stage to the previous stage of the carbonaceous material for the negative electrode of the nonaqueous electrolyte secondary battery finally obtained. That is, it means all the carbonaceous matter that has not finished the final process.
In the present specification, the “carbon precursor that is not meltable with respect to heat” means a resin that does not melt by pre-baking or main baking. That is, in the case of petroleum pitch or tar, coal pitch or tar, or a thermoplastic resin, it means a carbonaceous precursor that has been subjected to an infusibilization treatment described below. On the other hand, since the thermosetting resin does not melt even if pre-baking or main baking is performed as it is, no infusibilization treatment is required.

Since the carbonaceous material of the present invention is a non-graphitizable carbonaceous material, petroleum pitch or tar, coal pitch or tar, or thermoplastic resin is infusibilized to make it infusible to heat in the production process. It is necessary to perform processing. The infusibilization treatment can be performed by forming a crosslink on the carbon precursor by oxidation. That is, the infusibilization treatment can be performed by a known method in the field of the present invention. For example, it can be performed according to the procedure of infusibilization (oxidation) described later.

(Infusibilization process)
When petroleum pitch or tar, coal pitch or tar, or a thermoplastic resin is used as the carbon precursor, infusibilization is performed. The method of infusibilization treatment is not particularly limited, and can be performed using, for example, an oxidizing agent. The oxidizing agent is not particularly limited, but as the gas, O ₂ , O ₃ , SO ₃ , NO ₂ , a mixed gas obtained by diluting these with air, nitrogen or the like, or an oxidizing gas such as air is used. Can do. As the liquid, an oxidizing liquid such as sulfuric acid, nitric acid, or hydrogen peroxide, or a mixture thereof can be used. The oxidation temperature is not particularly limited, but is preferably 120 to 400 ° C, and more preferably 150 to 350 ° C. If the temperature is lower than 120 ° C., a sufficient crosslinked structure cannot be formed and the particles are fused in the heat treatment step. On the other hand, when the temperature exceeds 400 ° C., the decomposition reaction is more than the crosslinking reaction, and the yield of the obtained carbon material is lowered.

Calcination uses a non-graphitizable carbon precursor as a carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode. When pre-baking and main baking are performed, the temperature may be once lowered after the pre-baking, pulverized, and main baking may be performed. The pulverization step may be performed after the infusibilization step, but is preferably performed after preliminary firing.

The carbonaceous material of the present invention is produced by a step of pulverizing a carbon precursor and a step of firing the carbon precursor.

(Pre-baking process)
The pre-baking step in the present invention is performed by baking the carbon source at 300 ° C. or higher and lower than 900 ° C. Pre-firing removes volatile components such as CO ₂ , CO, CH ₄ , and H ₂ , and tar components, and reduces the generation of these components in the main firing, thereby reducing the burden on the calciner. . When the pre-baking temperature is less than 300 ° C., detarring becomes insufficient, and there is a large amount of tar and gas generated in the main baking process after pulverization, which may adhere to the particle surface. This is not preferable because it cannot be maintained and the battery performance is lowered. The pre-baking temperature is preferably 300 ° C. or higher, more preferably 500 ° C. or higher, and particularly preferably 600 ° C. or higher. On the other hand, when the pre-baking temperature is 900 ° C. or higher, the tar generation temperature range is exceeded, and the energy efficiency to be used is lowered, which is not preferable. Furthermore, the generated tar causes a secondary decomposition reaction, which adheres to the carbon precursor and may cause a decrease in performance, which is not preferable. Also, if the pre-baking temperature is too high, carbonization proceeds and the carbon precursor particles become too hard, and when pulverizing after pre-firing, it becomes difficult to pulverize such as scraping the inside of the pulverizer This is not preferable.
Pre-baking is performed in an inert gas atmosphere, and examples of the inert gas include nitrogen and argon. Pre-baking can also be performed under reduced pressure, for example, 10 kPa or less. The pre-baking time is not particularly limited, but can be performed, for example, in 0.5 to 10 hours, and more preferably 1 to 5 hours.

In order to obtain the carbonaceous material of the present invention, the rate of temperature increase in the pre-firing is preferably 1 ° C / h or more and 150 ° C / h or less, more preferably 5 ° C / h or more and 100 ° C / h or less, and 10 ° C / h or more. 50 ° C./h or less is more preferable. Carbon precursors with a true density (ρBt) determined by the butanol method of 1.55 g / cm ³ or more and less than 1.75 g / cm ³ have a large amount of tar generated during pre-firing, and gradually volatilize these volatile components. It is considered that a carbonaceous material having a suitable pore diameter can be prepared and a high discharge capacity is developed. However, the present invention is not limited by the above description.

(Crushing process)
The pulverization step is performed in order to make the particle size of the carbon precursor uniform. It can also grind | pulverize after carbonization by this baking. As the carbonization reaction proceeds, the carbon precursor becomes hard and it becomes difficult to control the particle size distribution by pulverization. Therefore, the pulverization step is preferably performed after preliminary calcination and before main calcination.
The pulverizer used for pulverization is not particularly limited. For example, a jet mill, a ball mill, a hammer mill, or a rod mill can be used. However, a jet mill having a classification function in that fine powder is generated less. Is preferred. On the other hand, when using a ball mill, a hammer mill, a rod mill or the like, fine powder can be removed by classification after pulverization.
Examples of classification include classification with a sieve, wet classification, and dry classification. Examples of the wet classifier include a classifier using a principle such as gravity classification, inertia classification, hydraulic classification, or centrifugal classification. Examples of the dry classifier include a classifier using the principle of sedimentation classification, mechanical classification, or centrifugal classification.

In the pulverization step, pulverization and classification can be performed using one apparatus. For example, pulverization and classification can be performed using a jet mill having a dry classification function.
Furthermore, an apparatus in which the pulverizer and the classifier are independent can be used. In this case, pulverization and classification can be performed continuously, but pulverization and classification can also be performed discontinuously.

(Main firing process)
The main firing step in the present invention can be performed according to a normal main firing procedure, and a carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode can be obtained by performing the main firing. The firing temperature is 900 to 1600 ° C. If the main calcination temperature is less than 900 ° C., many functional groups remain in the carbonaceous material and the H / C value becomes high, and the irreversible capacity increases due to reaction with lithium, which is not preferable. The lower limit of the main firing temperature of the present invention is 900 ° C. or higher, more preferably 1000 ° C. or higher, and particularly preferably 1100 ° C. or higher. On the other hand, if the main firing temperature exceeds 1600 ° C., the selective orientation of the carbon hexagonal plane increases and the discharge capacity decreases, which is not preferable. The upper limit of the main calcination temperature of the present invention is 1600 ° C. or less, more preferably 1500 ° C. or less, and particularly preferably 1450 ° C. or less.
The main firing is preferably performed in a non-oxidizing gas atmosphere. Examples of the non-oxidizing gas include helium, nitrogen, and argon, and these can be used alone or in combination. Furthermore, the main calcination can be performed in a gas atmosphere in which a halogen gas such as chlorine is mixed with the non-oxidizing gas. Moreover, this baking can also be performed under reduced pressure, for example, can also be performed at 10 kPa or less. Although the time for the main baking is not particularly limited, it can be performed, for example, in 0.1 to 10 hours, preferably 0.2 to 8 hours, and more preferably 0.4 to 6 hours.

(Manufacture of carbonaceous material from tar or pitch)
An example is given and demonstrated below about the manufacturing method of the carbonaceous material of this invention from a tar or a pitch.
First, the tar or pitch was subjected to a crosslinking treatment (infusibilization). The tar or pitch subjected to the crosslinking treatment is carbonized by subsequent firing to become a non-graphitizable carbonaceous material. Tar or pitch includes petroleum tar or pitch replicated during ethylene production, coal tar produced during coal carbonization, heavy component or pitch obtained by distilling off low boiling components of coal tar, tar or pitch obtained by liquefaction of coal Oil or coal tar or pitch can be used. Two or more of these tars and pitches may be mixed.

Specifically, as a method for infusibilization, there are a method using a crosslinking agent, a method of treating with an oxidizing agent such as air, and the like. When using a cross-linking agent, a carbon precursor is obtained by adding a cross-linking agent to petroleum tar or pitch, or coal tar or pitch and heating and mixing to proceed with a cross-linking reaction. For example, as the crosslinking agent, polyfunctional vinyl monomers such as divinylbenzene, trivinylbenzene, diallyl phthalate, ethylene glycol dimethacrylate, or N, N-methylenebisacrylamide that undergo a crosslinking reaction by radical reaction can be used. The crosslinking reaction with the polyfunctional vinyl monomer is started by adding a radical initiator. As the radical initiator, α, α ′ azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), lauroyl peroxide, cumene hydroperoxide, 1-butyl hydroperoxide, hydrogen peroxide, or the like can be used. .

Also, when the crosslinking reaction is advanced by treatment with an oxidizing agent such as air, it is preferable to obtain a carbon precursor by the following method. That is, to a petroleum pitch or coal pitch, a bicyclic to tricyclic aromatic compound having a boiling point of 200 ° C. or higher or a mixture thereof is added as an additive and heated and mixed, and then molded to obtain a pitch molded body. Next, the additive is extracted and removed from the pitch molded body with a solvent having low solubility with respect to pitch and high solubility with respect to the additive to form a porous pitch, which is then oxidized with an oxidizing agent, and then carbon precursor. Get the body. The purpose of the aromatic additive is to extract and remove the additive from the molded pitch molded body to make the molded body porous, to facilitate crosslinking treatment by oxidation, and to obtain a carbonaceous material obtained after carbonization. To make it porous. As said additive, it can select from 1 type, or 2 or more types of mixtures, such as naphthalene, methyl naphthalene, phenyl naphthalene, benzyl naphthalene, methyl anthracene, phenanthrene, or biphenyl, for example. The amount of the aromatic additive added to the pitch is preferably in the range of 30 to 70 parts by mass with respect to 100 parts by mass of the pitch.

* Mixing of pitch and additives is performed in a molten state by heating in order to achieve uniform mixing. The mixture of the pitch and the additive is preferably performed after being formed into particles having a particle diameter of 1 mm or less so that the additive can be easily extracted from the mixture. Molding may be performed in a molten state, or may be performed by a method such as pulverizing the mixture after cooling. Solvents for extracting and removing the additive from the mixture of pitch and additive include aliphatic hydrocarbons such as butane, pentane, hexane, or heptane, mixtures mainly composed of aliphatic hydrocarbons such as naphtha or kerosene, methanol, Aliphatic alcohols such as ethanol, propanol or butanol are preferred. By extracting the additive from the pitch and additive mixture molded body with such a solvent, the additive can be removed from the molded body while maintaining the shape of the molded body. At this time, it is presumed that a through hole for the additive is formed in the molded body, and a pitch molded body having uniform porosity is obtained.

Further, as a method for preparing the porous pitch formed body, the following method can be used in addition to the above method. Oil pitch or coal pitch or the like is pulverized to an average particle size (median diameter) of 60 μm or less to form a fine powder pitch, and then the fine powder pitch, preferably an average particle size (median diameter) of 5 μm or more and 40 μm or less. Can be compression-molded to form a porous compression-molded body. An existing molding machine can be used for compression molding, and specific examples include a single-shot vertical molding machine, a continuous rotary molding machine, and a roll compression molding machine, but are not limited thereto. The pressure at the time of compression molding is preferably 20 to 100 MPa as a surface pressure or 0.1 to 6 MN / m as a linear pressure, more preferably 23 to 86 MPa as a surface pressure or 0.2 to 3 MN / m as a linear pressure. m. The pressure holding time at the time of the compression molding can be appropriately determined according to the type of molding machine, the properties of the fine powder pitch, and the processing amount, but is generally within the range of 0.1 second to 1 minute. When compression molding a fine powdery pitch, a binder (binder) may be blended as necessary. Specific examples of the binder include water, starch, methylcellulose, polyethylene, polyvinyl alcohol, polyurethane, and phenol resin, but are not necessarily limited thereto. The shape of the porous pitch molded body obtained by compression molding is not particularly limited, and examples thereof include granular, columnar, spherical, pellet, plate, honeycomb, block, and Raschig rings.

In order to crosslink the resulting porous pitch, it is then oxidized with an oxidizing agent, preferably at a temperature of 120 to 400 ° C. As the oxidizing agent, O ₂ , O ₃ , NO ₂ , a mixed gas obtained by diluting these with air, nitrogen, or the like, or an oxidizing gas such as air, or an oxidizing liquid such as sulfuric acid, nitric acid, or hydrogen peroxide water is used. be able to. It is simple and economical to oxidize at 120 to 400 ° C. and carry out a crosslinking treatment using a gas containing oxygen such as air or a mixed gas of air and other gas such as combustion gas as an oxidizing agent. Is also advantageous. In this case, if the pitch has a low softening point, the pitch melts during oxidation, making it difficult to oxidize. Therefore, the pitch used preferably has a softening point of 150 ° C. or higher.
The carbon precursor subjected to the crosslinking treatment as described above is pre-fired and then carbonized at 900 ° C. to 1600 ° C. in a non-oxidizing gas atmosphere to obtain the carbonaceous material of the present invention. Can do.

(Manufacture of carbonaceous material from resin)
A method for producing a carbonaceous material from a resin will be described below with an example.
The carbonaceous material of the present invention can also be obtained by carbonizing at 900 ° C. to 1600 ° C. using a resin as a precursor. As the resin, a phenol resin, a furan resin, or the like, or a thermosetting resin obtained by partially modifying the functional group of these resins can be used. It can also be obtained by pre-calcining the thermosetting resin at a temperature lower than 900 ° C., if necessary, pulverizing, and carbonizing at 900 ° C. to 1600 ° C. If necessary, an oxidation treatment (infusibilization treatment) may be performed at a temperature of 120 to 400 ° C. for the purpose of accelerating the curing of the thermosetting resin, promoting the degree of crosslinking, or improving the carbonization yield. As the oxidizing agent, O ₂ , O ₃ , NO ₂ , a mixed gas obtained by diluting these with air, nitrogen, or the like, or an oxidizing gas such as air, or an oxidizing liquid such as sulfuric acid, nitric acid, or hydrogen peroxide water is used. be able to.
Furthermore, a carbon precursor obtained by subjecting a thermoplastic resin such as polyacrylonitrile or a styrene / divinylbenzene copolymer to infusibilization treatment can also be used. In these resins, for example, a monomer mixture obtained by mixing a radically polymerizable vinyl monomer and a polymerization initiator is added to an aqueous dispersion medium containing a dispersion stabilizer and suspended by stirring to suspend the monomer mixture into fine droplets. Then, it can be obtained by proceeding radical polymerization by raising the temperature. The obtained resin can be made into a spherical carbon precursor by developing a crosslinked structure by infusibilization treatment (oxidation treatment). The infusibilization treatment can be performed in a temperature range of 120 to 400 ° C., particularly preferably 170 to 350 ° C., more preferably 220 to 350 ° C. As the oxidizing agent, O ₂ , O ₃ , SO ₃ , NO ₂ , a mixed gas obtained by diluting these with air, nitrogen, or the like, or an oxidizing gas such as air, or an oxidizing property such as sulfuric acid, nitric acid, hydrogen peroxide water, or the like Liquid can be used. Thereafter, the carbon precursor that is infusible to heat as described above is pre-fired as necessary, and then pulverized and carbonized at 900 ° C. to 1600 ° C. in a non-oxidizing gas atmosphere, The carbonaceous material of the present invention can be obtained.
Although the pulverization step can be performed after carbonization, since the carbon precursor becomes hard as the carbonization reaction proceeds, it becomes difficult to control the particle size distribution by pulverization. It is preferable before the main baking later.

[2] Nonaqueous electrolyte secondary battery negative electrode The nonaqueous electrolyte secondary battery negative electrode of the present invention contains the carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode of the present invention.

(Manufacture of negative electrode)
In the negative electrode using the carbonaceous material of the present invention, a binder (binder) is added to the carbonaceous material, and an appropriate solvent is added and kneaded to form an electrode mixture. It can be produced by pressure molding after coating and drying. By using the carbonaceous material of the present invention, it is possible to produce an electrode having high conductivity without adding a conductive auxiliary agent. When preparing the agent, a conductive aid can be added. As the conductive assistant, conductive carbon black, vapor grown carbon fiber (VGCF), nanotube, etc. can be used, and the amount added varies depending on the type of conductive assistant used, but the amount added is too small. Since the expected conductivity cannot be obtained, it is not preferable, and too much is not preferable because the dispersion in the electrode mixture becomes worse. From such a point of view, the preferable ratio of the conductive auxiliary agent to be added is 0.5 to 10% by mass (where the amount of active material (carbonaceous material) + the amount of binder + the amount of conductive auxiliary agent = 100% by mass). More preferably, it is 0.5 to 7% by mass, particularly preferably 0.5 to 5% by mass. The binder is not particularly limited as long as it does not react with an electrolytic solution such as PVDF (polyvinylidene fluoride), polytetrafluoroethylene, and a mixture of SBR (styrene-butadiene rubber) and CMC (carboxymethylcellulose). Among them, PVDF is preferable because PVDF attached to the surface of the active material hardly inhibits lithium ion migration and obtains favorable input / output characteristics. In order to dissolve PVDF and form a slurry, a polar solvent such as N-methylpyrrolidone (NMP) is preferably used, but an aqueous emulsion such as SBR or CMC can also be dissolved in water. When the amount of the binder added is too large, the resistance of the obtained electrode is increased, which is not preferable because the internal resistance of the battery is increased and the battery characteristics are deteriorated. Moreover, when there is too little addition amount of binder, the coupling | bonding with negative electrode material particle | grains and a collector is insufficient, and it is unpreferable. The amount of the binder added is preferably 3 to 13% by mass, more preferably 3 to 10% by mass for the PVDF binder, although it varies depending on the type of binder used. On the other hand, a binder using water as a solvent is often used by mixing a plurality of binders such as a mixture of SBR and CMC, and the total amount of all binders used is preferably 0.5 to 5% by mass. The amount is preferably 1 to 4% by mass. The electrode active material layer is basically formed on both sides of the current collector plate, but may be on one side if necessary. A thicker electrode active material layer is preferable for increasing the capacity because fewer current collector plates and separators are required. However, the larger the electrode area facing the counter electrode, the better the input / output characteristics, and the thicker the active material layer. Too much is not preferable because the input / output characteristics deteriorate. The thickness of the active material layer (per side) is preferably 10 to 80 μm, more preferably 20 to 75 μm, and still more preferably 20 to 60 μm.

[3] Nonaqueous electrolyte secondary battery The nonaqueous electrolyte secondary battery of the present invention includes the negative electrode of the nonaqueous electrolyte secondary battery of the present invention.

(Manufacture of non-aqueous electrolyte secondary batteries)
When the negative electrode material of the present invention is used to form a negative electrode of a nonaqueous electrolyte secondary battery, other materials constituting the battery such as a positive electrode material, a separator, and an electrolytic solution are not particularly limited, and are nonaqueous solvents. Various materials conventionally used or proposed as a secondary battery can be used.

For example, as the positive electrode material, a layered oxide system (represented as LiMO ₂ , where M is a metal: for example, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , or LiNi _x Co _y Mo _z O ₂ (where x, y and z represent composition ratios), olivine system (represented by LiMPO ₄ , M is metal: for example, LiFePO _4, etc.), spinel system (represented by LiM ₂ O ₄ , M is a metal: for example, LiMn ₂ O _4, etc. The composite metal chalcogen compound is preferable, and these chalcogen compounds may be mixed if necessary.These positive electrode materials are molded together with an appropriate binder and a carbon material for imparting conductivity to the electrode, and are electrically conductive. The positive electrode is formed by forming a layer on the conductive current collector.

The nonaqueous solvent electrolyte used in combination of these positive electrode and negative electrode is generally formed by dissolving an electrolyte in a nonaqueous solvent. Examples of the non-aqueous solvent include organic solvents such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, diethoxyethane, γ-butyllactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, or 1,3-dioxolane. These can be used alone or in combination of two or more. As the electrolyte, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiCl, LiBr, LiB (C ₆ H ₅ ) ₄ , or LiN (SO ₃ CF ₃ ) ₂ is used. In secondary batteries, the positive electrode layer and the negative electrode layer formed as described above are generally immersed in an electrolytic solution with a liquid-permeable separator made of nonwoven fabric or other porous material facing each other as necessary. It is formed by. As the separator, a non-woven fabric usually used for a secondary battery or a permeable separator made of another porous material can be used. Alternatively, a solid electrolyte made of a polymer gel impregnated with an electrolytic solution can be used instead of or together with the separator.

The lithium ion secondary battery of the present invention is suitable as a battery (typically a lithium ion secondary battery for driving a vehicle) mounted on a vehicle such as an automobile.

The vehicle according to the present invention can be targeted without particular limitation, such as a vehicle normally known as an electric vehicle, a hybrid vehicle with a fuel cell or an internal combustion engine, and at least a power supply device including the battery, An electric drive mechanism that is driven by power supply from the power supply device and a control device that controls the electric drive mechanism are provided. Further, a power generation brake or a regenerative brake may be provided, and a mechanism for converting the energy generated by braking into electricity and charging the lithium ion secondary battery may be provided. Since the hybrid vehicle has a particularly low degree of freedom in battery volume, the battery of the present invention is useful.

Hereinafter, the present invention will be specifically described by way of examples, but these do not limit the scope of the present invention.

The physical property values (ρ _Bt , ρ _He , BET specific surface area, average particle diameter (D _v50 ), hydrogen / carbon atomic ratio (H / C) of the non-aqueous electrolyte secondary battery negative electrode of the present invention are as follows: d ₀₀₂ , charge capacity, discharge capacity, irreversible capacity, moisture absorption), including physical properties values described in this specification including examples are based on values obtained by the following methods It is.

(True density by the butanol method (ρ _Bt ))
The true density was measured by a butanol method according to a method defined in JIS R 7212. The mass (m ₁ ) of a specific gravity bottle with a side tube having an internal volume of about 40 mL is accurately measured. Next, the sample is placed flat on the bottom so as to have a thickness of about 10 mm, and its mass (m ₂ ) is accurately measured. Gently add 1-butanol to this to a depth of about 20 mm from the bottom. Next, light vibration is applied to the specific gravity bottle, and it is confirmed that large bubbles are not generated. Then, the bottle is placed in a vacuum desiccator and gradually evacuated to 2.0 to 2.7 kPa. Keep at that pressure for 20 minutes or more, and after the generation of bubbles has stopped, take it out, fill it with 1-butanol, plug it and immerse it in a constant temperature water bath (adjusted to 30 ± 0.03 ° C) for 15 minutes or more. Adjust the liquid level of 1-butanol to the marked line. Next, this is taken out, the outside is well wiped off and cooled to room temperature, and then the mass (m ₄ ) is accurately measured.

Next, the same specific gravity bottle is filled with only 1-butanol, immersed in a constant temperature water bath as described above, and after aligning the marked lines, the mass (m ₃ ) is measured. Moreover, distilled water excluding the gas that has been boiled and dissolved immediately before use is collected in a specific gravity bottle, immersed in a constant temperature water bath in the same manner as described above, and after aligning the marked line, the mass (m ₅ ) is measured. ρ _Bt is calculated by the following equation.

At this time, d is the specific gravity (0.9946) of water at 30 ° C.

(True density by the helium method (ρ _He ))
Measurement of [rho _{the He} used a Shimadzu dry automatic densimeter Accupyc II1340. The sample was previously dried at 200 ° C. for 5 hours or more and then measured. Using a 10 cm ³ cell, a 1 g sample was placed in the cell, and the measurement was performed at an ambient temperature of 23 ° C. Purge number is 10 times, of which, using the average value of 5 times was confirmed to agree to within 0.5% by repeated measurement volume value (n = 5), and a [rho _{the He.}

The measuring device has a sample chamber and an expansion chamber, and the sample chamber has a pressure gauge for measuring the pressure in the chamber. The sample chamber and the expansion chamber are connected by a connecting pipe having a valve. A helium gas introduction pipe having a stop valve is connected to the sample chamber, and a helium gas discharge pipe having a stop valve is connected to the expansion chamber.

Specifically, the measurement was performed as follows.
The volume of the sample chamber (V _CELL ) and the volume of the expansion chamber (V _EXP ) are measured in advance using a calibration sphere with a known volume. The sample is placed in the sample chamber, fills the system with helium, the system pressure at that time and P _a. Then closing the valve, is increased to a pressure P ₁ added sample chamber only helium gas. After that, when the valve is opened and the expansion chamber and the sample chamber are connected, the system pressure decreases to P ₂ due to expansion.
At this time, the volume of the sample (V _SAMP ) is calculated by the following equation.

Therefore, if the sample mass is W _SAMP , the density is

It becomes.

(Specific surface area by nitrogen adsorption (BET))
An approximate expression derived from the BET expression is described below.

Using the above approximate expression, at liquid nitrogen temperature, 1-point method by nitrogen adsorption seek v _m by (relative pressure x = 0.2), was calculated a specific surface area of the sample by the following equation.

In this case, _{v m} is the adsorption amount necessary for forming a monomolecular layer on the surface of the sample ^(cm 3 / g), v the adsorption amount of the measured ^(cm 3 / g), x is a relative pressure.

Specifically, using a “Flow Sorb II2300” manufactured by MICROMERITICS, the amount of nitrogen adsorbed on the carbonaceous material at the liquid nitrogen temperature was measured as follows. Fill the sample tube with a carbonaceous material pulverized to a particle size of about 1 to 20 μm, and cool the sample tube to -196 ° C while flowing a mixed gas of helium: nitrogen = 80:20 to adsorb nitrogen to the carbonaceous material. Let The sample tube is then returned to room temperature. At this time, the amount of nitrogen desorbed from the sample was measured with a thermal conductivity detector, and the amount of adsorbed gas v was obtained.

(Atomic ratio of hydrogen / carbon (H / C))
Measurement was performed in accordance with the method defined in JIS M8819. From the mass ratio of hydrogen and carbon in the sample obtained by elemental analysis with a CHN analyzer, the hydrogen / carbon atom number ratio was obtained.

(Average layer surface spacing by X-ray diffraction method (d ₀₀₂ ))
The carbonaceous material powder was filled in the sample holder and measured by a symmetrical reflection method using X'Pert PRO manufactured by PANalytical. The scanning range was 8 <2θ <50 °, and the applied current / applied voltage was 45 kV / 40 mA. An X-ray diffraction pattern was obtained using a CuKα ray (λ = 1.5418Å) monochromated by a Ni filter as a radiation source. . Correction was performed using the diffraction peak of the (111) plane of the high-purity silicon powder for standard substances. The wavelength of the CuKα ray is set to 0.15418 nm, and d ₀₀₂ is calculated by the Bragg formula.

λ: X-ray wavelength, θ: diffraction angle

(Average particle diameter by laser diffraction method ( _Dv50 ))
Three drops of a dispersing agent (cationic surfactant “SN Wet 366” (manufactured by San Nopco)) are added to about 0.01 g of the sample, and the dispersing agent is acclimated to the sample. Next, after adding pure water and dispersing with ultrasonic waves, the complex refractive index parameter (real part-imaginary part) is set to 2.0- with a particle size distribution measuring instrument (“SALD-3000S” manufactured by Shimadzu Corporation). A particle size distribution in the range of 0.08 to 3000 μm was obtained with 0.1i. From the obtained particle size distribution, the average particle size _Dv50 was _{defined as the} particle size with a cumulative volume of 50%.

(Moisture absorption)
Before the measurement, the carbonaceous material was vacuum-dried at 200 ° C. for 12 hours, and then 1 g of this carbonaceous material was spread on a petri dish having a diameter of 9.5 cm and a height of 1.5 cm so as to be as thin as possible. . After being left in a constant temperature and humidity chamber controlled to a constant atmosphere at a temperature of 25 ° C. and a humidity of 50% for 100 hours, the container is removed from the constant temperature and humidity chamber, and a Karl Fischer moisture meter (Mitsubishi Chemical Analytech / CA-200) is used. ) Was used to measure the amount of moisture absorption. The temperature of the vaporization chamber (Mitsubishi Chemical Analytech / VA-200) was 200 ° C.

(Active material dope-dedope test)
Using the carbonaceous materials 1 to 10 and the comparative carbonaceous materials 1 to 6 obtained in the examples and comparative examples, the following operations (a) to (d) are performed to form a negative electrode and a nonaqueous electrolyte secondary battery. And the electrode performance was evaluated.

(A) Electrode preparation 94 parts by mass of the above carbonaceous material, 6 parts by mass of polyvinylidene fluoride (“KF # 9100” manufactured by Kureha Co., Ltd.) and a negative electrode mixture made into a paste by adding NMP, and the above carbonaceous material 4 A negative electrode mixture prepared by adding water to 96 parts by mass, 3 parts by mass of SBR, and 1 part by mass of CMC was prepared. The electrode mixture was uniformly applied on the copper foil. After drying, it was punched out from a copper foil into a disk shape having a diameter of 15 mm and pressed to obtain an electrode. The amount of carbonaceous material in the electrode was adjusted to about 10 mg.

(B) Production of test battery The carbonaceous material of the present invention is suitable for constituting the negative electrode of a non-aqueous electrolyte secondary battery, but the discharge capacity (de-doping amount) and irreversible capacity (non-desorption) of the battery active material. In order to accurately evaluate the amount of doping) without being affected by variations in the performance of the counter electrode, a lithium secondary battery is configured using the electrode obtained above, using lithium metal with stable characteristics as a counter electrode, Its characteristics were evaluated.

The lithium electrode was prepared in a glove box in an Ar atmosphere. A 16 mm diameter stainless steel mesh disk is spot-welded to the outer lid of a 2016 coin-sized battery can, and then a 0.8 mm thick metal lithium sheet is punched into a 15 mm diameter disk shape. To be an electrode (counter electrode).

Using the electrode pair thus produced, the electrolyte solution was LiPF ₆ at a ratio of 1.4 mol / L in a mixed solvent in which ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 2: 2. A coin-type non-aqueous electrolyte system of 2016 size in an Ar glove box using a polyethylene-made gasket as a separator, using a borosilicate glass fiber fine pore membrane having a diameter of 19 mm as a separator A lithium secondary battery was assembled.

(C) Measurement of battery capacity About the lithium secondary battery of the said structure, the charge / discharge test was done at 25 degreeC using the charge / discharge test apparatus ("TOSCAT" by Toyo System). Lithium doping reaction on the carbon electrode was performed by the constant current constant voltage method, and dedoping reaction was performed by the constant current method. Here, in a battery using a lithium chalcogen compound as a positive electrode, the lithium doping reaction to the carbon electrode is “charging”, and in a battery using a lithium metal as the counter electrode like the test battery of the present invention, This doping reaction is referred to as “discharge”, and the naming of the lithium doping reaction to the same carbon electrode differs depending on the counter electrode used. Therefore, for the sake of convenience, the lithium doping reaction on the carbon electrode will be described as “charging”. Conversely, “discharge” is a charging reaction in the test battery, but is referred to as “discharge” for convenience because it is a dedoping reaction of lithium from the carbonaceous material. The charging method adopted here is a constant current constant voltage method. Specifically, constant current charging was performed at 0.5 mA / cm ² until the terminal voltage reached 0.050 V, and the terminal voltage reached 0.050 V. Thereafter, constant voltage charging was performed at a terminal voltage of 0.050 V, and charging was continued until the current value reached 20 μA. At this time, the value obtained by dividing the supplied amount of electricity by the mass of the carbonaceous material of the electrode was defined as the charge capacity (mAh / g) per unit mass of the carbonaceous material. After completion of charging, the battery circuit was opened for 30 minutes and then discharged. The discharge was a constant current discharge at 0.5 mA / cm ² and the final voltage was 1.5V. A value obtained by dividing the quantity of electricity discharged at this time by the mass of the carbonaceous material of the electrode is defined as a discharge capacity (mAh / g) per unit mass of the carbonaceous material. The irreversible capacity is calculated as charge capacity-discharge capacity. The test battery produced using the same sample was measured three times (n = 3), and the measured values were averaged to determine the charge / discharge capacity and the irreversible capacity. Further, the value obtained by dividing the discharge capacity by the charge capacity was multiplied by 100 to obtain the efficiency (%). This is a value indicating how effectively the active material has been used.

(D) The slope of the discharge curve The discharge capacity X (Ah / g) corresponding to 0.2 V to 1.1 V is obtained on the basis of the lithium reference electrode, divided by the potential difference 0.9 (V), and the discharge curve A slope of 0.9 / X (Vg / Ah) was calculated.

Example 1
A 70 kg petroleum pitch with a softening point of 205 ° C. and an H / C atomic ratio of 0.65 and 30 kg of naphthalene are charged into a 300 liter pressure vessel equipped with a stirring blade and an outlet nozzle, and heated, melted and mixed at 190 ° C. After cooling to 80 to 90 ° C., the inside of the pressure vessel was pressurized with nitrogen gas, and the contents were extruded from the outlet nozzle to obtain a string-like molded body having a diameter of about 500 μm. Subsequently, this string-like molded body was pulverized so that the ratio (L / D) of the diameter (D) to the length (L) was about 1.5, and the obtained crushed material was heated to 93 ° C. The solution was poured into an aqueous solution in which 53% by mass of polyvinyl alcohol (saponification degree 88%) was dissolved, stirred and dispersed, and cooled to obtain a spherical pitch molded body slurry. After most of the water was removed by filtration, naphthalene in the pitch formed body was extracted and removed with n-hexane having a mass about 6 times that of the spherical pitch formed body. The porous spherical pitch thus obtained was heated to 240 ° C. while passing through heated air using a fluidized bed, oxidized at a temperature of 240 ° C. for 1 hour, and insoluble to heat. Spherical oxidized pitch was obtained.
Next, 100 g of porous spherical oxidation pitch was put in a vertical tubular furnace having a diameter of 50 mm, heated to 600 ° C. at a rate of 100 ° C./h, held at 600 ° C. for 1 hour, pre-baked, and carbon precursor Got the body. Pre-baking was performed in a nitrogen atmosphere with a flow rate of 5 L / min. The obtained carbon precursor was pulverized to obtain a powdery carbon precursor having an average particle size of 4.8 μm. Subsequently, 10 g of this powdery carbon precursor was put into a horizontal tubular furnace having a diameter of 100 mm, heated to 1200 ° C. at a heating rate of 250 ° C./h, held at 1200 ° C. for 1 hour, and subjected to main firing, Carbonaceous material 1 was prepared. The main firing was performed in a nitrogen atmosphere with a flow rate of 10 L / min.

(Example 2)
A carbonaceous material 2 was obtained in the same manner as in Example 1 except that the nitrogen flow rate during main firing was changed to 1 L / min.

Example 3
A carbonaceous material 3 was obtained in the same manner as in Example 1 except that the oxidation temperature of the porous spherical pitch was changed to 230 ° C. and the pulverized particle size of the carbon precursor was changed to 9.5 μm.

Example 4
A carbonaceous material 4 was obtained in the same manner as in Example 1 except that the oxidation temperature of the porous spherical pitch was changed to 210 ° C. and the pulverized particle size of the carbon precursor was changed to 12.0 μm.

(Example 5)
A carbonaceous material 5 was obtained in the same manner as in Example 3 except that the oxidation temperature of the porous spherical pitch was changed to 205 ° C.

(Example 6)
A carbonaceous material 6 was obtained in the same manner as in Example 1 except that the pulverized particle size of the carbon precursor was changed to 3 μm.

(Example 7)
A carbonaceous material 7 was obtained in the same manner as in Example 1 except that the pulverized particle size of the carbon precursor was changed to 14 μm.

(Example 8)
A coal pitch having a softening point of 205 ° C. and an H / C atomic ratio of 0.49 was pulverized by a counter jet mill (Hosokawa Micron Corporation / 100-AFG) to obtain a powdery pitch having an average particle size of 6.2 μm. Then, this powdery pitch was put into a muffle furnace (Denken Co., Ltd.), and infusible treatment was carried out by maintaining at 260 ° C. for 1 hour while circulating air at 20 L / min, to obtain an infusible pitch. 100 g of the infusibilized pitch obtained was put in a crucible, heated at a rate of 50 ° C./h up to 600 ° C. in a vertical tubular furnace with a diameter of 50 mm, pre-fired by holding at 600 ° C. for 1 hour, carbon A precursor was obtained. Pre-baking was performed in a nitrogen atmosphere with a flow rate of 5 L / min, and the crucible was opened. 10 g of carbon precursor is placed in a horizontal tubular furnace having a diameter of 100 mm, heated to 1200 ° C. at a heating rate of 250 ° C./h, held at 1200 ° C. for 1 hour, and subjected to main firing to prepare carbonaceous material 8 did. The main firing was performed in a nitrogen atmosphere with a flow rate of 10 L / min.

Example 9
A carbonaceous material 9 was obtained in the same manner as in Example 8 except that the infusibilization temperature was changed to 240 ° C. and the pulverized particle size of the carbon precursor was 9.0 μm.

(Example 10)
An aqueous dispersion medium of 250 g of 4% methylcellulose aqueous solution and 2.0 g of sodium nitrite was prepared in 1695 g of water. On the other hand, a monomer mixture composed of 500 g of acrylonitrile and 2.9 g of 2,2′-azobis-2,4 dimethylvaleronitrile was prepared. An aqueous dispersion medium was added to this monomer mixture, and the mixture was stirred for 15 minutes at 2000 rpm with a homogenizer to granulate fine droplets of the monomer mixture. An aqueous dispersion medium containing fine droplets of this polymerizable mixture was charged into a polymerization can equipped with a stirrer (10 L) and polymerized at 55 ° C. for 20 hours using a warm bath. The obtained polymerization product was filtered from the aqueous phase, dried and sieved to obtain a spherical synthetic resin having an average particle size of 40 μm.
The obtained synthetic resin was oxidized at a temperature of 250 ° C. for 5 hours while passing heated air to obtain a heat-insoluble precursor. This was fired in a nitrogen gas atmosphere at a heating rate of 100 ° C./h up to 800 ° C. and then pulverized by a counter jet mill (Hosokawa Micron Corporation / 100-AFG) to obtain a powdery carbon precursor. Next, 10 g of this carbon precursor is placed in a horizontal tubular furnace having a diameter of 100 mm, heated to 1250 ° C. at a heating rate of 250 ° C./h, and held at 1250 ° C. for 1 hour to perform main firing, thereby producing a carbonaceous material. 10 was obtained.

(Example 11)
In the same manner as in Example 4, except that the carbonaceous material 4 obtained in Example 4 was made of a negative electrode mixture prepared by adding water to 96 parts by mass, 3 parts by mass of SBR, and 1 part by mass of CMC. evaluated.

(Comparative Example 1)
The oxidation temperature of the porous spherical pitch was changed to 270 ° C., the pulverized particle size of the carbon precursor was changed to 10 μm, and this powdery carbon precursor was calcined at 1200 ° C. under reduced pressure of 1.3 × 10 ⁻⁵ kPa for 1 hour. A comparative carbonaceous material 1 was obtained in the same manner as in Example 1 except that.

(Comparative Example 2)
30 g of a powdery carbon precursor similar to that in Comparative Example 1 is charged into a cylindrical crucible having a sample container diameter of 40 mm and a height of 60 mm, the inlet is sealed with a carbon plate, and the gas generated during the carbonization reaction stays in the crucible. Carbonization was performed in the state. After charging the crucible in the electric furnace, vacuuming the inside of the system and substituting with nitrogen gas, the inside of the electric furnace is made into a nitrogen gas atmosphere, heated to 1200 ° C. at a rate of 250 ° C./h, and then at 1200 ° C. for 1 hour. Holding, a comparative carbonaceous material 2 was obtained.

(Comparative Example 3)
A comparative carbonaceous material 3 was obtained in the same manner as in Example 1 except that the firing temperature of the main firing was 1450 ° C.

(Comparative Example 4)
A comparative carbonaceous material 4 was obtained in the same manner as in Example 1 except that the firing temperature of the main firing was set to 800 ° C.

(Comparative Example 5)
Comparative carbonaceous material 5 was obtained in the same manner as in Comparative Example 2 except that the oxidation temperature of the porous spherical pitch was 223 ° C.

(Comparative Example 6)
Comparative carbonaceous material 6 was obtained in the same manner as in Comparative Example 2 except that the oxidation temperature of the porous spherical pitch was 215 ° C.

Table 1 shows the characteristics of the carbonaceous materials obtained in Examples and Comparative Examples, and the measurement results of the electrodes produced using the carbonaceous materials and the battery performance.

The carbonaceous materials of Examples 1 to 11 have a true density (ρ _Bt ) of 1.55 g / cm ³ or more and less than 1.75 g / cm ^{3 and a} discharge capacity of 0.05 A to 1.5 V of 180 Ah / g or more. The slope 0.9 / X of the discharge curve from 0.2 V to 1.1 V was in the range of 0.75 (Vg / Ah) or less. This indicates that the slope of the discharge curve per volume in the potential range most used in the in-vehicle lithium ion secondary battery of 0.2 V to 1.1 V is gentle, and thus the charging range of around 50%. In the practical state used in the above, the potential difference between the negative electrode and the positive electrode is kept high and exhibits a high discharge capacity per volume. Moreover, the amount of moisture absorption was low. Therefore, Examples 1 to 10 were provided with a high discharge capacity per volume and storage characteristics in a practical range.

On the other hand, in Comparative Examples 1, 2, and 4, the true density (ρ _Bt ) is less than 1.55 g / cm ³ and the voids are large in the crystal structure. The amount was high. In Comparative Example 2, the discharge capacity at 0.05 V to 1.5 V was low. In Comparative Examples 3, 5, and 6, the true density (ρ _Bt ) was included in the scope of the present invention, but the discharge capacity at 0.05 V to 1.5 V was low. In Comparative Examples 2, 3, 5, and 6, since the slope of the discharge curve (0.9 / X) is large, sufficient capacity cannot be secured in the slope region in the practical range.

Claims (8)

1. The true density (ρ _Bt ) determined by the butanol method is 1.55 g / cm ³ or more and less than 1.75 g / cm ³ , and the discharge capacity of the negative electrode at 0.05 V to 1.5 V based on the lithium reference electrode is 180 mAh / g or more. Yes,
   Slope of discharge curve 0.9 / X (Vg / Ah) calculated from discharge capacity X (Ah / g) corresponding to 0.2 V to 1.1 V on the basis of lithium reference electrode and potential difference 0.9 (V) Is 0.75 (Vg / Ah) or less, and the moisture absorption after storage for 100 hours in a 25 ° C. and 50% RH air atmosphere is 1.5 wt% or less. Carbon for non-aqueous electrolyte secondary battery negative electrode Quality material.
2. The carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to claim 1, wherein a true density (ρ _He ) obtained by a helium substitution method is 1.76 g / cm ³ or more.
3. [rho _{the He} and [rho _Bt and the ratio (ρ _He / ρ _Bt) is a non-aqueous electrolyte secondary battery negative electrode carbonaceous material according to claim 1 or 2 is 1.10 or more.
4. When the specific surface area (BET) (m ² / g) determined by the BET method by adsorption of nitrogen gas and the average particle diameter (unit: μm) are D _v50 , the calculation formula “6 / (D _v50 × ρ _Bt 4) The specific surface area ratio (BET / CALC) to the specific surface area (CALC) (m ² / g) obtained from “)” is more than 5.5. The nonaqueous electrolyte secondary according to any one of claims 1 to 3 Carbonaceous material for battery negative electrode.
5. The carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to any one of claims 1 to 4, wherein the average particle size is 1 µm or more and 15 µm or less.
6. A negative electrode for a non-aqueous electrolyte secondary battery comprising the carbonaceous material for a non-aqueous electrolyte secondary battery negative electrode according to any one of claims 1 to 5.
7. A nonaqueous electrolyte secondary battery comprising the negative electrode for a nonaqueous electrolyte secondary battery according to claim 6.
8. A vehicle equipped with the nonaqueous electrolyte secondary battery according to claim 7.